This invention relates generally to the field of medical instrumentation and more specifically to detection of defects of the retina, the optic nerve, and the brain""s visual pathways.
A large number of medical ailments manifest themselves as defects in a patient""s visual field. Patients suffering from macular degeneration, anterior ischemic optic neuropathy (AION), glaucoma, optic neuritis, detached retina, macular edema, central or branch retinal artery occlusion, some genetic impairments, and brain tumors may experience losses in visual acuity and visual field.
Non-invasive methods to measure a patient""s visual field have been developed. For example, perimetry and campimetry provide information pertaining to the borderline between seeing and non-seeing areas within a patient""s visual field.
Visual field tests employing visual field test patterns, such as an Amsler grid, have been developed to give a qualitative analysis of a patient""s visual field. However such tests do not provide data of sufficient resolution or precision to perform a quantitative analysis of a patient""s condition.
Recent developments of testing methods using visual field test patterns have included adjusting a patient""s perception of the contrast levels within a visual field test pattern. For example, a method disclosed in U.S. Pat. No. 4,818,091, the disclosure of which is hereby incorporated by reference, requires the use of eyeglasses with polarized lenses to adjust the apparent contrast level of an Amsler grid.
These methods suffer from a variety of problems. Some methods require a patient to endure a long and boring testing process during which time the patient""s concentration may lag because of fatigue. Other methods, while capable of being quickly performed, do not provide the spatial and contrast resolution required for high quality quantitative analysis.
Therefore, a need exists for a method that is quicker, simpler and more revealing than existing methods for characterizing the visual field. The present invention meets such need.
A method and apparatus for electronically performing a visual field test for a patient is provided. A visual field test pattern including a peripheral fixation point is displayed to the patient on an electronic display device and the patient""s responses to the visual field test pattern are recorded. A visual field representation is generated from the patient""s responses. The visual field representation is then used as an input into a variety of diagnostic processes. In one embodiment of the invention, a series of visual field test patterns of varying contrast are presented to a patient in order to construct a three-dimensional visual field representation wherein contrast sensitivity is plotted as the Z-axis.
In one aspect of the invention, a visual field measurement apparatus includes an electronic visual field test pattern display device for display of visual field test patterns including a peripheral fixation point to a patient, a patient response input device for recording a patient""s response to a visual field test pattern, and a tester operably coupled to both for conducting the visual field measurement.
A patient views a visual field test pattern and selects areas in the visual field test pattern where the visual field test pattern is missing or distorted. The patient selects these visual field test pattern areas using a touch screen mounted on the electronic display device. A series of visual field test patterns of differing contrasts are presented to the patient and the patient""s responses are recorded.
A visual field representation generator operably coupled to the tester generates a visual field representation using the patient""s responses. The visual field representation is used in a variety of diagnostic processes.
In another aspect of the invention, a distributed visual field measurement system is created using a tester Web server operably coupled to a browser via the Internet. The tester Web server serves pages to the browser implementing a visual field measurement system.
In another aspect of the invention, visual field representations are correlated with known causes of visual field defects and stored in a diagnostic database operably coupled to a diagnostic server accessible via the Internet. A clinician sends a visual field representation to the diagnostic server. The diagnostic server uses an AI engine to determine a diagnosis using the visual field representation.